Dense Matters:Astronomers Peek Inside Neutron Star

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Starlyte 2

Astronomers have snatched a peek at the innards of a neutron star, combining a series of observations to pin down the type of matter squeezed into the ultra-dense stellar ball.

The approach is expected to enable future astronomers to gain glimpses of the stuff inside other neutron stars and boost their understanding of matter, energy and the fundamental particles that make up the universe.

"Neutron stars are a sort of cosmic lab in a sense that the material at their centers is so dense it can't be reproduced on Earth," said study leader Tod Strohmayer in a telephone interview. "We can't get a piece of this material and examine it ourselves."

About the size of a city, a neutron star is the remnant of an exploded star whose matter is so compressed, the protons and electrons within its atoms fuse into neutrons. A teaspoon of the dense stuff would weigh about a billion tons on Earth.

Understanding the internal structure of a neutron star would allow scientists to determine the object's basic properties, explained Lars Hernquist, an astronomer with the Harvard-Smithsonian Center for Astrophysics unaffiliated with Strohmayer's study.

Strohmayer's star, part of a star system called EXO 0748-676, sits in the southern sky constellation Volans (the Flying Fish) about 30,000 light-years away from Earth. One light-year is the distance light travels in a year, or roughly 6 trillion miles (10 trillion kilometers).

The neutron star has a radius of about 7 miles (11.5 kilometers) and a mass about 1.75 times of the Sun. It is also part of a binary system; it strips gas from a companion star and then blows the material outward in repetitive thermonuclear explosions.

Strohmayer, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, studied the neutron star with colleague and graduate student Adam Villarreal of the University of Arizona. The pair presented their research before the High Energy Astrophysics Division of the American Astronomical Society during a meeting last week in New Orleans.